This invention relates to a process for telomerization and/or oligomerization of acyclic conjugated diolefins of 4-6 carbon atoms using catalytically active complexes of palladium and triaryl phosphines.
It is conventional to utilize palladium complexes for linear telomerization and/or oligomerization of conjugated diolefins. The catalytically active palladium complexes contain, as ligands, tertiary phosphines, phosphites, or arsines, which may be mixed with other organic compounds, e.g., maleic anhydride or p-benzoquinone. Suitable known cocatalysts are, inter alia, organic bases, for example, quaternary ammonium hydroxides, as disclosed in U.S. Pat. No. 3,769,352, incorporated herein by reference.
Oligomerization, of which the simplest case is dimerization, refers to reaction of a diolefin with another molecule of diolefin. Telomerization refers to the reaction of diolefins with H-acidic compounds, such as alcohols, water, phenols, carboxylic acids, or amines.
Conditions required for oligomerization and/or telomerization depend on the catalyst system and the reactants. (Takahashi et al, Bulletin of the Chemical Society of Japan, Vol. 41, 454-460 (1968).)
To attain high selectivity in the telomerization reaction low reaction, temperatures are advantageous. In the telomerization process, high selectivity is generally achieved by maintaining the concentration of the diolefin at a low level with respect to the H-acidic compound. This can be done, for example, by feeding the diolefin continuously into the reaction mixture as it is consumed. Favorable conditions can be realized only if the catalysts and reactants employed lead to adequately high reaction rates. Otherwise, economically useful conversion rates are obtained only under conditions less favorable for selectivity, i.e., the reactants are contacted with catalyst for a rather long period of time at high temperatures and under high pressures.
The reaction products are separated from the catalyst by distillation at the end of the oligomerization and/or telomerization reaction.
Conditions used during the workup step depend primarily on the activity and stability of the catalysts employed. A distinction can be made, with corresponding advantages and disadvantages, between conditions used with highly active, low-stability catalysts, as disclosed, for example, in DOS (German Unexamined Laid-Open Application) No. 1,955,933 and the corresponding U.S. Pat. No. 3,670,032, and those used with low-activity catalysts, as disclosed by Takahashi et al., "Tetrahedron Letters" 26 (1967):2451.
Although a variety of more or less expensive methods having various disadvantages are known, a genuine need has existed for a process which:
(a) takes place with high space-time yields and selectivities;
(b) permits multiple reuse of palladium catalyst; and
(c) produces, for otherwise identical reactions, identical product compositions from recycled catalysts.
It is an object of the invention to provide a process combining the advantages of known catalyst systems without the disadvantages connected therewith.